Electric current converting circuit



Dec. 1, 1970 SHINICHIRO OGAWA ETAL ELECTRIC CURRENT CONVERTING CIRCUIT Filed Sept. 16, 1968 5 3 F/g.4 E *2 l H 2 IL' H E #1? 4 2 4 Z 4 Q 5 Z3 1 mm m SHINIC BY TOSHIY INVENTOR O OGA l MATSUDA ATTORNEY United States Patent O 3,544,815 ELECTRIC CURRENT CONVERTING CIRCUIT Shinichiro Ogawa and Toshiyuki Matsuda, Tokyo, Japan,

assignors to Honeywell Inc., Minneapolis, Minn., a corporation of Delaware Filed Sept. 16, 1968, Ser. No. 759,945 Claims priority, application Japan, Sept. 18, 1967, 42/ 59,393 Int. Cl. H03k 3/26 US. Cl. 307-270 1 Claim ABSTRACT OF THE DISCLOSURE A first serial connection comprises a first resistor, a first transistor and a first load. A second serial connection comprises a second load, a second transistor, a second resistor and a third load. The first serial connection is connected parallel to the second serial connection. A current of a magnitude proportional to the magnitude of the current in the first load is obtained in the second and third loads.

BACKGROUND OF THE INVENTION This invention relates to an electric current converting circuit and more particularly to an electric current converting circuit in a direct current operational circuit in which one of the terminals of a plurality of loads or operational circuits is connected to the fixed potential of a power source.

SUMMARY OF THE INVENTION In the invention of subject application, a first serial circuit comprised of a first resistor, a first transistor and a first load is connected across a constant current source and a second serial circuit comprised of a second load, a second transistor, a second resistor and a third load is connected across a current source. When the voltage across the base electrode and the emitter electrode of the first transistor is made substantially equal to the voltage across the base electrode and the emitter electrode of the second transistor, the current in the second load and the third load can be made proportional to the current in the first load.

Therefore, the object of this invention is to obtain an electric current converting circuit which is capable of supplying current to the above loads simultaneously.

BRIEF DESCRIPTION OF THE DRAWING FIGS. 1 and 2 are the connection diagrams showing the basic form of the electric current converting circuit of this invention, and

FIGS. 3 through 6 are the connection diagrams showing embodiments of the electric current converting circuit of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, the emitter of a PNP type transistor Q is connected to a terminal 1 and the base of an NPN type transistor Q through a resistor R and the emitter of the transistor Q is connected to a terminal 4 and the base of the transistor Q through a resistor R The collector of the transistor Q is connected to the negative terminal of a constant current power source 11 and the negative terminal of a power source E through a terminal 2 and a load or an operational circuit Z and the positive terminal of constant current power source 11, is connected to terminal 1.

The collector of the transistor Q is connected to the positive terminal of a power source E through a terminal 3 and a load or an operational circuit Z and the negative terminal of the power source E is connected to the positive terminal of the power source E and a load or a terminal of an operational circuit Z Another terminal of the load Z is connected to terminal 4, and a joint between the emitter of the transistor Q and the resistor R forms a terminal 5.

The circuit surrounded by terminals 1, 2, 3 and 4 is named a four-terminal network N. The resistors R anr R function to determine the conversion characteristics.

In the circuit shown in FIG. 1, if it is assumed that constant current power source 11 generates a current 1 in the direction shown in the figure, a voltage V across terminals 1 and 4 becomes as follows:

1 1+ be1 where:

R =resistance of resistor R V =voltage across base and emitter of transistor Q The transistors Q and Q have both high gains and the base current is smaller than the collector current; accordingly, it is possible to assume that the collector current of the transistor Q is equal to the current 1,.

If the current supplied from the battery E to the circuit consisting of the load Z the transistor Q the resistor R and the load Z is represented by a current 1 the voltage V across terminals 1 and 4 is shown by the following formula.

be2+ 2 2 where:

V =voltage across base and emitter of transistor Q R =resistance of resistor R As it is possible to make the difference between the voltages V and V extremely small, the following relation can be obtained.

l1R1=I2R2 By changing the above equation, it is obtained that The above equation shows that the current 1 which is obtained by multiplying the constant current I flowing through the load Z, by the multiplication factor R /R flows through the loads Z and Z The direction connecting the base-emitter junction of the transistors Q and Q is arranged in such a direction that the above voltages V and V compensate each other against the heat of their own generation and the variations of ambient temperature. Consequently, the variations in the voltages V and V due to the change of temperature cancel each other and no error will take place in the circuit.

Thus, the connection of two transistors of mutually different polarities makes it possible to reduce the conversion errors compared with the case where only one transistor is used.

As stated above, from across terminals 1 and 4 and from across terminals 5 and 4 can be taken out respectively different voltage outputs I R +V and I R Instead of the transistors Q and Q if a composite transistor circuit consisting of a combination of two or more transistors is employed, the conversion accuracy can be improved as the input impedance becomes high and the current amplification factor increases. In addition, as it is possible to make the collector current small in the first stage of the composite transistor circuit, the compensation for the voltage across the base and emitter against the self-generated heat and ambient temperature variation will be extremely improved.

FIG. 2 shows the method to connect the various components in case the polarities of constant current power source 11 in FIG. 1 are reversed.

FIG. 3 shows a connection diagram in case the power source E is inserted between terminal 2 and the load Z in FIG. 1. This type of connection is employed when it is more desirable to supply power separately from an inverter as the power source E in such a common direct current power source system as impresses a direct current 24 volt voltage to individual instruments.

FIG. 4 shows an arrangement Where the loads 2,; and Z are connected in parallel in addition between terminals 4 and 5 in FIG. 1.

FIG. 5 shows a connecting method capable of taking out a current output in parallel using a transistor which does not especially compensate for the voltage across the base and emitter in FIG. 1.

FIG. 6 shows a connecting method capable of increasing current load by connecting in series-parallel a plurality of the four-terminal networks in FIG. 1.

As stated above, the advantages of this invention are that in the current conversion circuit of this invention, a high conversion accuracy can be obtained, it is possible to simplify the power supply composition for the amplifier to be used as a load and the whole operational circuit, and it is possible to supply current simultaneously to a maximum of three loads in the basic conversion circuit.

What is claimed is:

1. An electric current converting circuit comprising:

a pair of transistors having mutually different polarities, a pair of resistors connecting the emiters of the respective transistors to the bases of the other transistors, a constant current power source and a first load con- 5 nected in series with a circuit composed of one of the transistors and one of the resistors, a second load, a current power source and a third load connected in series with a circuit composed of the other of the transistors and the other of the resistors, and

10 a separate current power source connecting the first load to the third load.

References Cited UNITED STATES PATENTS 3,271,528 9/1966 Vallese 33()-30 3,383,612 5/1968 Harwood 330-22 DONALD D. FORRBR, Primary Examiner R. C. WOODBRIDGE, Assistant Examiner U.S. Cl. X.R. 

